Jet fuel is basically kerosene. You could run a home-made jet on kerosene. I’ve heard that some people have run jet engines on gasoline, but that they have to be careful with it. Gasoline is much more volatile than Jet-A and could burn out the engine.
One of the more important things to remember about rotorcraft is that they are inherently unstable. That’s what makes them so much fun to fly. 
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Huh? What does MacCready have to do with this? Are you suggesting that I’ll end up in the arctic and have to face the Thing? Besides, Mac was a chopper pilot.
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I’d been leaning that way-less materials, weight and work involved, and less to go wrong. And if the engine, the fuel tank, the prop, etc fall off, you’re still attached to a parachute.
I’m well aware of the problems and risks. I plan on subjecting the thing to every kind of stress test you can name before actually going up in it.
Spiny Norman mentioned Junkyard Wars. It was indeed very inspiring. The thing to remember though, is that these guys are all experienced pilots.
The first thing you need to know when you want to build a flying machine is aerodynamics. It’s true that if you have enough power, you can make a barn door fly. But would you want to fly it? Anyway, power is expensive. Better to build something that doesn’t need much of it to fly. And if you have, as you say, no knowledge of aerodynamics, then you’d better build some models first if you are serious.
I don’t know anything about powered parachutes, so I can’t give any of my non-expert advice on them.
There’s a reason why ultralights tend to look similar to each other: the deign works! You see to basic layouts: delta wings with no tail, and straight wings with a tail. When I was a kid back in the 1970s I built model hang gliders. I just took some balsa, some tissue, and a coat hanger and put them together with no other experience than building Guillow’s models. They flew well, except when I caught an alligator lizard and tried to fly it. I couldn’t quite get the weight and balance right. But if a pre-teen can design and build a little glider that works the first time (without a payload, anyway), then a delta wing might be a design to look at.
The normal “airplane” layout flies better, I think; but it will be more difficult to build. But I do think it will be more forgiving.
Aerodynamics. There are four forces at work on an airplane: thrust, drag, lift and gravity. You need to balance these forces. You need enough thrust to overcome drag, so you can develop enough lift to overcome gravity (weight). Power is always an issue with GA pilots. Most light planes make you choose between a full load of passengers and a full load of fuel. One or the other often has to be left behind!
Since you are asking about a flying machine, it seems the logical place to start is with Lift. I’m sure you are familiar with the airfoil shape. There are many, many different airfoils. Some work better at low speeds (which is what you;ll want) and others work better at high speeds. You can find FUNDAMENTALS OF FLIGHT FM 1-230 (the Army field manual), which has equations to figure out lift. But the FAA or ASA manuals are easier to find. They’ll give you an overview of aerodynamics, but without the equations. So you’ll probably have to experiment with models first.
Junkyard Wars can give you an idea of how to bodge together an airframe, but since those guys were experienced it will take you a lot more experimentation.
In any case, let’s say you build a wing. You want it to be light and strong. DougC mentions using spruce, which would probably be the best choice. (But don’t try to build the Wright Flyer, which was not a good flying machine.) Here’s where the Guillow’s models may help you out. They are designed to be stable since there is not pilot; and light, since they’re powered by a rubber band and have to glide without damagine themselves. Model airplanes are often built directly on the plans (an option which you will not have). You lay down the spars and the leading and trailing edges, then attach the ribs. For a real airplane your ribs will need to be built up and not solid. (But for a Junkyard Flyer you may be able to get by with foamcore.) Weight is critical. Building it strong, but also light will be a constant fight.
The tail surfaces will be much simpler to make.
Next, you’ll need somthing to hold everything together: a fuselage. Your model-building will have shown you the approximate layout. Again, it needs to be light; but it also needs to be structurally sound.
So now you have somthing that can make lift. You need power so you can overcome drag and generate that lift to overcome gravity. The problem is that engines are heavy. You might not be able to find an engine that’s light enough that has enough power. And remember that most ground-based engines turn at around 5,200 rpm for peak power. A prop needs to turn at about 2,300 rpm. Youll need a reduction drive. And speaking of props, making them is a bit of a “lost art”. You’re better off buying one.
I could go on and on and on about this, but here’s a better idea: Don’t build your flying machine yet. Hie thee to someplace where you can learn to fly an actual ultralight aircraft. Broomstick can give you pointers there. I understand the desire to design and build your own aircraft from scratch. Hell, I’d like to give it a go myself! But you’ll be better off buying a real ultralight. Get lessons. Learn how to fly an ultralight. Try different designs. If you really want to build one from scratch, then you should know what you’re doing.
PS to Broomstick:
I think there are cheap building methods and materials that can be used to make a “proof of concept” aircraft. I think it would be fun to experiment just to see if I could do it. But yeah, I agree that it’s not something I’d want to risk my life in as an “everyday use” machine.
Of course, certified designs are tested to distruction.
Just out of curiosity - why do you want to build the engine from scratch? Why not just use, say, a gas chainsaw motor and adapt it for a prop?
Re-Testing To Destruction
Wouldn’t bother me. If I can build a working ultralite for next to nothing, I can certainly build a second one using the same plans and materials.
Re-Chainsaw
I just don't see how this would work. Horsepower aside, you need a two stroke motor.Most chainsaws DO use two-stoke motors Doc.
Some of the guys who are into building model airplanes do this, but I don’t know if such an engine would be powerful enough to propell a human through the air.
MacCready designed and built (with a team) the Gossamer aircraft - Condor and Albatross - which were both successful human-powered aircraft weighing less than 100 lbs. The power output of the engine/pilot was estimated at 1/4 hp on average. The first plane successfully flew a figure-eight course, the second crossed the English channel entirely on pedal power. Both planes would easily fall under the Part 103 regulation for ultralights, although I think both pre-dated them. But MacCready is the current Master of Lightweight Aircraft, just as Rutan is the current Master of Cannards (and he’s gunning for Master of Civilian Space Travel).
There are a LOT of different building techniques out there. I’d recommend you find some ultralighters/lightplane homebuilders and ask them about their aircraft. There ARE ultralights that use foam as part of the wing structure… can’t recall the model offhand. Skypup? There are wooden ones, cloth-and-tube, metal… a lot of different ways to get off the ground. You really need to see these in real life. Hook up with builders so you can learn not just construction techniques but safety concerns that have sometimes been learned the very hard way by others. Volunteer to help them out, you can learn a lot that way.
As for small jets… my local airport has been known to sell Jet A (which, indeed, is a fancy form of kerosene) to guys running model jets and other somewhat unconventional things - but they do have some rules about who they will and won’t sell to.
There have been attempts to power UL’s with chainsaw motors, with very mixed success. The problem isn’t so much getting off the ground, it’s dealing with asymmetrical thrust when an engine quits and the others keep going. That’s why multi-engine UL’s have pretty much been abandoned. If you aren’t a pilot already stick to a single engine to start. If you are a pilot - get multi-engine lessons.
If you build something that’s basically a decent glider you’ll need less horsepower to get off the ground, which means a smaller engine and less weight.
You MIGHT even be able to pick up a fully functional paraglider used for the price it would cost to build one from scratch - folks frequently grow bored with their limitations after awhile and want to change to something else. If you do this, take along a person with experience with that form of flying machine who has no financial stake in the deal to help you inspect it.
Which brings me to another point - UL’s of any sort are limited flying machines. Don’t fly them in high wind (that may be defined as low as “more than 10 mph”), don’t horse around. If you grow bored with what you have don’t push the limits too hard - sell it and get something more suited to what you want to do.
You can also buy wrecks for dirt cheap and scavenge them for parts. However, I would recommend tossing anything bloodstained - you’ll never get it out, and you might cause damage trying. Not that all wrecks have biohazard potential, but some do.
I seriously suggest that you get a subscription to or buy a copy of Kit Planesmagazine. They carry it at any Barns and Noble magazine rack. While much of the magazine is dedicated to articles about building commercially available kits and ads for the kits, they also carry articles and plans for projects similar to what you describe. Unlike the ads for aircraft plans in Popular Mechanics, I believe that the ones there are actually capable of being built and flying successfully.
I seriously suggest you head down to your local Hobby shop and pick up a model airplane kit. Do not get an ARF (almost ready to fly) or a RTF (ready to fly) model – you need the building experience. Once you get this mastered, scratch build a model of your ultralight, and work out all the kinks at that stage. I know this seems like a lot to go through to build a plane, but aerodynamic rules and principles are nothing to scoff at – it’s taken us years of research to reach the point we’re at now with aviation. There are rules you must follow for an aircraft to fly successfully, and you need to get real familiar with those rules.
I’m an experienced R/C modeler who has been flying and building models for over 15 years, and I still don’t think I’m ready to scratch build an ultralight (although I’ve thought about it several times). Start small, and work your way up from there. It might just save your life.
Hope this helps.
Reading this thread just makes me glad I’m not the only one that builds themselves harebrained contraptions.
As for chainsaw engines, maybe but I’d think you’d want more than one of them. And they’re a bit awkward to adapt to things. I would assume an old lawnmower engine would be your best bet if you want to keep it cheap and stay in the air (are they two stroke?).
To echo other folks, get some tested plans. You don’t want a poorly placed joint to snap mid flight and send you to your darwin award winning doom. Good Luck.
You could try cluster ballooning… it’s pretty low-tech and cheap…
MaCready-
I’m familiar with the Gossamers. I was joking. MacCready was also the name of a character in John Carpenter’s The Thing.
Kits-
Of course it makes more sense to buy a kit. But, this isn’t what I want to do. Building a kit does demonstrate skill. But, it’s still too conventional for me.
Used ULs-
Again, not interested. Buying something requires no skill at all. I have no skills to trade.
RC Planes- With what money?
Lawnmower engines come in two and four-stroke versions in various horsepower ratings.
As someone who has been a member of the EAA, and active in the homebuilt community for a long time, let me say this:
Don’t do it.
Not on the cheap. Not with materials you find at garage sales. All aluminum is not created equal. Materials that don’t have a paper trail may have been damaged through heat, or stress, or just manufactured to poor tolerances. If you try to make a paraplane out of some surplus cloth (even ex-parachute dacron), you may find out the hard way that it was left in the sun five years ago and has broken down under UV bombardment… I once saw a fabric-covered airplane you could punch holes through with your finger, the cloth was so degraded.
Always remember, you are betting your life on this. you say you plan to ‘stress test’ the heck out of it. If you aren’t an engineer, how do you know what stresses will be on it in the first place? Are you going to test every bolt, every fitting, every wire? You can’t. The act of stress testing destroys the material. That’s why airplane builders buy expensive materials of known quality.
Who’s going to flight test your design? Just gliding it down a hill at successively high altitudes is the test mechanism that early pioneers used - and died trying. How are you going to test for things like flutter or stall characteristics?
Aircraft building from known designs is not to be taken lightly. Actually designing your own airplane is a task for someone with a lot of money, a good engineering background, and a competant test pilot or two.
And besides, I highly doubt you’ll be able to build your machine for as little as you think. If you can’t afford plans for an airplane, you can’t afford an airplane. Period. No matter how good a scrounger you are, you’ll have a couple of thousand dollars into your paraplane at a minimum. You might as well go and buy one of the commercial paraplanes - you can probably find a used powered paraglider complete with a fiberglass fuselage and landing gear for around $5,000. Maybe less.
If you can’t afford that, you can’t afford to fly. If you still want a cool project, how about building a submarine, or an amphibious ATV, or something like that? Something that won’t kill you if it goes badly.
I intend to go for the simplest possible design. This lowers cost and the amount of things that can go wrong.
The Delaware river is just a few miles away. A few of my other projects are water based.
I made a full list of my projects around here somewhere-OTOMH theremin, rc blimp, 1 seater pedal boat, bathysphere, various LED projects,
Wouldn’t it be cool to cover a car totally in tiny different colored LEDs so you could change the color of the car and display moving advertising logo animations on the sides so local businesses would pay you?
(yeah its kind of a hijack but it’s too neat not to share!)
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- I found a page once that showed the inside of a WWI plane–without the fabric covering in place. It was, quite frankly, rather frightening in how little materials went into its construction. Except for the main wing spar, most of the wood used was strips about as big around as your index finger. The fuselage for instance had four “corner” strips, and then diagonals run between them evert couple feet. There was a small platform for the seat to be attached to, and no floor–just pedals to rest your feet on. Search out some good sources for this type of construction, just to see how light they were built… and then imagine flying around, shooting at things and being shot at in one…
- I found a page once that showed the inside of a WWI plane–without the fabric covering in place. It was, quite frankly, rather frightening in how little materials went into its construction. Except for the main wing spar, most of the wood used was strips about as big around as your index finger. The fuselage for instance had four “corner” strips, and then diagonals run between them evert couple feet. There was a small platform for the seat to be attached to, and no floor–just pedals to rest your feet on. Search out some good sources for this type of construction, just to see how light they were built… and then imagine flying around, shooting at things and being shot at in one…
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- Ehhh, you’d want to buy stock aluminum, if not real aircraft-grade, at least new stock T6. Chairs are made out of 4042 or other softer weaker alloys, often recycled…
- And most lawnmowers I see now run at ~3600 RPM’s. For a home-made prop you’d want to make it really big with lots of blades and turn it really slow. So a straight engine–>prop conection isn’t going to work for that…
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